The U.S. Supreme Court ruled on Monday that a University of Arizona police officer has immunity from being sued by a woman he shot in 2010.

In a decision unattributed to any one justice, the court noted that use of excessive-force cases need to be analyzed one-by-one considering the specific facts of each case. The opinion quoted case law that said, "An officer 'cannot be said to have violated a clearly established right unless the right's contours were sufficiently definite that any reasonable official in the defendant's shoes would have understood he was violating it.'"

But Justice Sonia Sotomayor did not mince words when she responded in her dissent that "Such a one-sided approach to qualified immunity transforms the doctrine into an absolute shield for law enforcement officers, gutting the deterrent effect of the Fourth Amendment."

The Fourth Amendment of the U.S. Constitution protects against unreasonable searches and seizures and demands that law enforcement have probable cause before acting.

Case began in 2010

The case in question goes back to May 2010, when university Police Corporal Andrew Kisela and a rookie officer responded to a welfare check on a woman hacking at a tree with a kitchen knife in a Tucson neighborhood. When they arrived, they saw Amy Hughes brandishing a knife while standing about six feet away from her roommate on the other side of a chain link fence from the officers.

Hughes ignored or did not hear Kisela's orders to drop the knife, and so he dropped to the ground and shot her four times through the fence, according to a court document. Hughes survived, and she sued Kisela for negligence and a civil rights violation, alleging he had used excessive force.

Upon investigation, it was determined that Hughes suffered from mental illness; the roommate claimed that she had the situation under control.

The lawsuit was originally filed in Pima County Superior Court in 2011, but was moved into U.S. District Court in Tucson because of the civil rights claim. A judge there granted summary judgment to Kisela in 2013, ruling that he had immunity from prosecution as a police officer having to make a life-or-death decision in a split second.

Justice Sotomayor: Decision 'sends an alarming signal'

The Supreme Court majority noted that it did not even have to consider whether Kisela violated the Fourth Amendment because, again quoting case law, "Qualified immunity attaches when an official's conduct does not violate clearly established statutory or constitutional rights of which a reasonable person would have known."

In her dissent, which was joined by Justice Ruth Bader Ginsburg, Sotomayor countered that two other officers on the scene refrained from shooting.

"But not Kisela," she wrote. "He thought it necessary to use deadly force, and so, without giving a warning that he would open fire, he shot Hughes four times, leaving her seriously injured.

"If this account of Kisela’s conduct sounds unreasonable, that is because it was. And yet, the Court today insulates that conduct from liability under the doctrine of qualified immunity, holding that Kisela violated no 'clearly established law.'"

In her conclusion, Sotomayor added that the "… decision is not just wrong on the law; it also sends an alarming signal to law enforcement officers and the public. It tells officers that they can shoot first and think later, and it tells the public that palpably unreasonable conduct will go unpunished."

Although Hughes vs. Kisela was a case out of Tucson, the matter of officer-involved shootings is particularly relevant in Maricopa County, where already this year, law enforcement officers have shot 22 people, killing 13 of them, according to a running tally kept by The Arizona Republic.

By contrast, according to numbers of fatal police shootings maintained by The Washington Post, there have been no fatal shootings by police in New York City and only one in Chicago so far this year.

In 2017, law enforcement in Maricopa County shot 43 people, killing 25 (compared to 10 in New York City and 8 in Chicago), and 45 in 2016, killing 27.

All officer-involved shootings in the county are reviewed by the Maricopa County Attorney's Office. In recent years, only two police officers have been charged with crimes related to shootings. One pleaded guilty to manslaughter and the other was acquitted by a jury.